Four peptides decrease human colon adenocarcinoma cell number and DNA synthesis via cyclic GMP.
BACKGROUND: Mortality from colon cancer is significant with an expected 30,350 colon cancer deaths in 2005 with current treatment(s). Long-acting natriuretic peptide, vessel dilator, kaliuretic peptide, and atrial natriuretic peptide have significant anticancer effects in breast and pancreatic adenocarcinomas. AIM OF STUDY: Whether these peptide hormones have anticancer effects in colon adenocarcinoma cells and whether these effects are specifically mediated by cyclic GMP has not been determined. METHODS: These peptide hormones were evaluated for anticancer effects in human colon adenocarcinoma cells and to determine whether their anticancer effects are specifically mediated by cyclic GMP. RESULTS: There was a 89-97% decrease (p <0.001 for each) in colon adenocarcinoma cells within 24 h with 1 mM of these peptide hormones. There was a significant (p <0.05) decrease in human colon cancer cell number with each 10-fold increase in concentration from 1 to 1,000 microM (i.e., 1 mM) of these four peptide hormones without any proliferation in the 3 d following this decrease. These same hormones decreased DNA synthesis 65-83% (p <0.001). Cyclic GMP antibody inhibited 75- 80% of these peptides' ability to decrease colon adenocarcinoma cell number and inhibited 92-96% of their DNA synthesis effects and 97% of cyclic GMP's effects. Western blots revealed that for the first time natriuretic peptide receptors (NPR) A and C were present in colon adenocarcinoma cells. CONCLUSIONS: Four peptide hormones eliminate up to 97% of colon cancer cells within 24 h with their DNA effects specifically mediated by cyclic GMP.